Recommended Trailer Wiring To Charge Battery And Use Solar Panels

Updated 04/26/2017 | Published 04/25/2017

Products Featured in This Question

40 Amp In-Line Circuit Breaker - Perpendicular Mount Bracket

(95)

$9.72

10 Gauge Wire - Blue Primary - Per Foot

(102)

$1.86

Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 40 Amp

(85)

$540.00

Firestone Fuse Circuit Tap Kit

(38)

$20.98

Starter Solenoid - SPST - 12 Volt - 100 Amp - Continuous Duty - Grounded

(12)

$34.34

Question:

Hello and thank you for such a helpful website. I have a small tear trailer with a solar system and single 12v deep cycle battery. During heavy usage e.g. lots of video editing on my laptop, plus cloudy days, Ive come to realize that my solar system just isnt enough to keep the trailer battery topped off. Which led me here to figure out how to charge my trailer battery with my tow vehicle. Unfortunately my TV and TT are set up with a flat 4-way, but I have a spare Anderson plug and so Ive thought about buying the wire to run from TV to TT. Ive read through several QandAs and found this one to be helpful and simple enough question-64598. My concern with this method is, what keeps the trailer battery from being overcharged? Would it essentially become a parallel battery bank between the TV/TT while connected through the Anderson plug with ignition on, and thats what keeps it from overcharging? If this is the case, do I need to be concerned about having different batteries in parallel, deep cycle in the trailer and a standard battery in my vehicle?

asked by: Jonathan

Expert Reply:

To wire your vehicle battery 12V to charge a trailer battery, I recommend using a 40 amp In-Line Circuit Breaker - Perpendicular Mount Bracket # 9510 along with # 10-1-1 to wire your trailer connection. In order not to drain your vehicle battery, I recommend you use the Battery Isolation Solenoid # PK5231201 to only allow the trailer to draw power when the vehicle is running.

You will need to use an ignition-controlled circuit in your truck to activate the solenoid. The radio circuit is often used for such purposes. You will need a fuse tap to access the switching function on this circuit; you can use part # F2526 from Firestone. This plugs into the fuse socket for your radio and connects to the center post on the solenoid. 12V power from the tow vehicle battery connects to either the left or right terminal and the power output exits the other side.

From your 12V trailer connection on the trailer, to allow you to use both solar and battery power, I recommend using the Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1240D. This will allow you to charge and maintain your 12V deep cycle trailer battery. It uses maximum power point tracking technology to acieve the most effiecient charge from your olar panels and eliminates the need for other regulators. It will keep your battery or batteries at peak charge without overcharging or undercharging. It also keeps you informed of the charging process. I've attached a photo to assist.